Blind fasteners are well known, and comprise devices insertable from one side through a hole in a member, and having means to anchor the device on the distal side of the hole. A screw-threaded component may be included, to tighten the device to the member. Such fasteners are utilised where access is available from one side only, and may for example clamp members together or be used to provide an anchorage. Typically a blind fastener includes a proximal side screw-threaded component having a screw-threaded distal (or blind) side anchorage arranged for close fitting passage through a hole. Once through the hole, the distal side anchorage changes form so as to resist withdrawal thereof, whereupon the proximal side component is tightened to firmly attach the fastener. The distal side fastener may for example comprise a folding component which is adapted to pass through the hole in folded form, and open out on the distal side to a diameter larger than the hole.